// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// TODO(rdsmith): This class needs to delegate URLRequest::Delegate methods
// to the net/ embedder for correct implementation of authentication.
// Specifically, this class needs the embedder to provide functionality
// corresponding to
// URLRequest::Delegate::{OnAuthRequired,OnCertificateRequested}.

#ifndef NET_URL_REQUEST_SDCH_DICTIONARY_FETCHER_H_
#define NET_URL_REQUEST_SDCH_DICTIONARY_FETCHER_H_

#include <memory>
#include <string>

#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/threading/non_thread_safe.h"
#include "net/base/sdch_manager.h"
#include "net/url_request/url_fetcher_delegate.h"
#include "net/url_request/url_request.h"
#include "url/gurl.h"

namespace net {

class BoundNetLog;
class URLRequest;
class URLRequestThrottlerEntryInterface;

// This class is used by embedder SDCH policy object to fetch
// dictionaries. It queues requests for dictionaries and dispatches
// them serially, implementing the URLRequest::Delegate interface to
// handle callbacks (but see above TODO). It tracks all requests, only
// attempting to fetch each dictionary once.
class NET_EXPORT SdchDictionaryFetcher : public URLRequest::Delegate,
                                         public base::NonThreadSafe {
public:
    typedef base::Callback<void(const std::string& dictionary_text,
        const GURL& dictionary_url,
        const BoundNetLog& net_log,
        bool was_from_cache)>
        OnDictionaryFetchedCallback;

    // The consumer must guarantee that |*context| outlives this object.
    explicit SdchDictionaryFetcher(URLRequestContext* context);
    ~SdchDictionaryFetcher() override;

    // Request a new dictionary fetch.  The callback will be called
    // only if the dictionary is successfully fetched. Returns true if a
    // request for |dictionary_url| has been scheduled, and false otherwise.
    virtual bool Schedule(const GURL& dictionary_url,
        const OnDictionaryFetchedCallback& callback);

    // Request a dictionary fetch from cache only.  The callback will be called
    // only if the dictionary is successfully fetched. Returns true if a request
    // for |dictionary_url| has been scheduled, and false otherwise.
    virtual bool ScheduleReload(const GURL& dictionary_url,
        const OnDictionaryFetchedCallback& callback);

    // Cancel any in-progress requests.
    virtual void Cancel();

    // Implementation of URLRequest::Delegate methods.
    void OnReceivedRedirect(URLRequest* request,
        const RedirectInfo& redirect_info,
        bool* defer_redirect) override;
    void OnResponseStarted(URLRequest* request) override;
    void OnReadCompleted(URLRequest* request, int bytes_read) override;

private:
    enum State {
        STATE_NONE,
        STATE_SEND_REQUEST,
        STATE_RECEIVED_REDIRECT,
        STATE_SEND_REQUEST_PENDING,
        STATE_READ_BODY,
        STATE_READ_BODY_COMPLETE,
        STATE_REQUEST_COMPLETE,
    };

    class UniqueFetchQueue;

    // Schedule implementation. Returns true if a request for |dictionary_url| has
    // been added to the queue, and false otherwise.
    bool ScheduleInternal(const GURL& dictionary_url,
        bool reload,
        const OnDictionaryFetchedCallback& callback);

    // Null out the current request and push the state machine to the
    // next request, if any.
    void ResetRequest();

    // State machine implementation.
    int DoLoop(int rv);
    int DoSendRequest(int rv);
    int DoReceivedRedirect(int rv);
    int DoSendRequestPending(int rv);
    int DoReadBody(int rv);
    int DoReadBodyComplete(int rv);
    int DoCompleteRequest(int rv);

    State next_state_;
    bool in_loop_;

    // A queue of URLs that are being used to download dictionaries.
    std::unique_ptr<UniqueFetchQueue> fetch_queue_;

    // The request, buffer, and consumer supplied data used for getting
    // the current dictionary.  All are null when a fetch is not in progress.
    std::unique_ptr<URLRequest> current_request_;
    scoped_refptr<IOBuffer> buffer_;
    OnDictionaryFetchedCallback current_callback_;

    // The currently accumulating dictionary. Stored as a unique_ptr so all memory
    // it consumes can be easily freed, as it gets quite big, and
    // std::string::clear() may not free memory.
    std::unique_ptr<std::string> dictionary_;

    // Store the URLRequestContext associated with the owning SdchManager for
    // use while fetching.
    URLRequestContext* const context_;

    DISALLOW_COPY_AND_ASSIGN(SdchDictionaryFetcher);
};

} // namespace net

#endif // NET_URL_REQUEST_SDCH_DICTIONARY_FETCHER_H_
